program light;
var
 o:array [1..2000000] of boolean;
 n:longint;
 f1,f2:text;

procedure init;
begin
 assign(f1,'light.in'); reset(f1);
 assign(f2,'light.out'); rewrite(f2);
 readln(f1,n);
 fillchar(o,sizeof(o),false);
end;

function pd(x:boolean):boolean;
begin
 if x=true then pd:=false
 else pd:=true;

end;

procedure play;
var  a:double; flag,t,i,j:longint;
begin
 for i:=1 to n do begin
  readln(f1,a,t);
  for j:=1 to t do
   o[trunc(a*j)]:=pd(o[trunc(a*j)]);
 end;
 for i:=1 to 2000000 do
  if o[i] then begin flag:=i; break; end;
 writeln(f2,flag);
 close(f2);

end;


begin
 init;
 play;
end.